I once interviewed a watermelon farmer when he said something surprising: Rather than chill his, he liked to leave them to bake in the summer sun for hours. The heat, he said, brings out floral, almost tropical flavors, stuff you’d never tasted in a fruit you’ve had a thousand times. I didn’t buy it—after all, cold watermelon on a hot day is one of the truest pleasures of life. But I tried it, and sure enough, he was right; the flavors were all o...